Spark plug boot

ABSTRACT

A high frequency electromagnetic radiation suppression shield surrounding adjacent ends of a spark plug lead wire and a spark plug and the means connecting the spark plug lead wire and the spark plug, comprising a silicone rubber boot having a metal screen integrally molded therein, which screen extends through one end of the boot and into engagement with the spark plug shell whereby the shell provides an electrical ground for the screen. The boot may be either straight or assume the angle made between the adjacent ends of the spark plug lead wire and the spark plug, and the boot may be either a single molded member or may be built up of one or two cylindrical portions connected by a generally circular end cap.

United States Patent 1 Berry 1 1 SPARK PLUG BOOT [76] Inventor: Norman 11. Berry. 49 Cambridge.

Pleasant Ridge. Mich. 48069 221 Filed: Mar. 19.1973

211 Appl.No.:342,384

[52] US. Cl 174/35 SM; 123/148 P; 174/35 TS [51] Int. Cl. "05k 5/00 [58] Field of Search 174/35 MS. 35 SM. 35 R.

174/77 S, 35 TS: 339/26. 143 S 136 C, 149 S; 123/143 R. 143 C. 148 P. 169 R. 169 PAzl69 PH; 313/134. 135. 137

[56] References Cited UNITED STATES PATENTS 7 1987.755 l/1935 Skaer et a1. 123/148 P 2.323.399 7/1943 Jacobi 174/35 SM 3.487.186 12/1969 Johnson et a1. 174/35 MS X [4 1 Apr. 29, 1975 Primary Eratrflner-Darrell L. Clay Attorney. Agent. or Firm-Whittemore. Hulbert & Belknap [57] ABSTRACT A high frequency electromagnetic radiation suppression shield surrounding adjacent ends of a spark plug lead wire and a spark plug and the means connecting the spark plug lead wire and the spark plug. comprising a silicone rubber boot having a metal screen integrally molded therein. which screen extends through one end of the boot and into engagement with the spark plug shell whereby the shell provides an electrical ground for the screen. The boot may be either straight or assume the angle made between the adjacent ends of the spark plug lead wire and the spark plug, and the bootmay be either a single molded member or may be built up of one or two cylindrical portions connected by a generally circular end cap.

6 Claims,v 5 Drawing Figures SPARK PLUG BOOT BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to suppression of high frequency radiation created on sparking of spark plugs such as in automobile ignition circuits and refers more specifically to a silicone boot constructed to surround adjacent ends of a spark plug lead wire and a spark plug and the means connecting the spark plug and spark plug lead wire having a metal screen molded therein, which screen extends through one end of the boot and into contact with the spark plug shell whereby a ground is provided for the high frequency shield.

2. Description of the Prior Art The closest known prior art is the Berry US. Pat. No. 3,686,607 in which a high frequency radiation suppression shield is positioned around a molding housing a radiation suppression resistor positioned between adjacent ends of a spark plug lead wire and a spark plug. In the prior structure, a metal screen is supported from a cylinder having a hexagon cross section adapted to fit over the base of a spark plug by means of a connecting strip between the cylinder and the screen. Such structure, while somewhat effective, has the disadvantage of being a separable article subject to being lost. Further. the high frequency shield disclosed in-this prior patent is exposed and therefore subject to damage. Also, the grounding of the high frequency shield in this prior structure is through the connecting strip and the hexagonal cylinder into the base of the spark plug, and since the hexagonal cylinder is a slip-fit on the spark plug base. the ground connection for the shield of the prior high frequency radiation suppression shields has not always been satisfactory.

SUMMARY OF THE INVENTION In accordance with the present invention, a high frequency radiation suppression shield comprising a metal screen molded into a silicone boot is adapted to fit snugly over the adjacent ends of a spark plug lead wire and a spark plug, the suppressor resistor positioned between the adjacent spark plug lead wire and spark plug ends, and the insulating material therefor. The metal screen extends through the end of the boot and engages the base of the spark plug to provide a positive ground connection for the high frequency boot.

The boot having the metal screen molded therein may be a single member or may be built up of one or more cylindrical members, one of which has the screen molded therein, and a circular cap therefor. Also, the high frequency radiation suppression shield constructed in accordance with the invention may be either straight or assume the angle made between the ad jacent ends of the spark plug lead wire and the spark plug.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of a spark plug, spark plug lead wire, radiation suppression resistor and means for connecting the spark plug, spark plug lead wire and radiation suppression resistor, and a high frequency radiation suppression shield constructed in accordance with the invention positioned over the radiation suppression resistor, the adjacent ends of the spark plug lead wire and spark plug, and the connecting means therefor.

FIG. 2 is a longitudinal section view of the high frequency radiation suppression shield. spark plug, spark plug lead wire, radiation suppression resistor and structure connecting them illustrated in FIG. 1. taken substantially on the line 2-2 in FIG. 1.

FIG. 3 is an enlarged portion of the section view of FIG. 2.

FIG. 4 is a partly broken away elevation view of a spark plug lead wire. spark plug and radiation suppression resistor and means for connecting them together. with the spark plug lead wire and spark plug at right angles to each other. and a modified high frequency radi-' ation suppression boot constructed in accordance with the invention in assembly therewith.

FIG. 5 is a longitudinal section view of a spark plug, spark plug lead wire. radiation suppression resistor and means for connecting them together with a modified high frequency radiation suppression shield in assembly therewith.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIG. 2, the high frequency radiation suppression shield of the invention is in assembly with a spark plug 12. the adjacent end of a spark plug lead wire 14, and a radiation suppression resistor 16 positioned between the adjacent ends of the spark plug 12 and spark plug lead wire 14. The spark plug 12 is secured in an engine block 18, while the spark plug lead wire 14 is in the usual automobile ignition circuit. not shown in further detail herein.

The spark plug 12 includes the metal base part or shell having the threaded end 22, and the electrodes 24 and 26. The shell 20 also includes the hexagonal nut portion 28 useful in screwing the spark plug 12 into the engine block 18. The spark plug 12 further includes the ceramic insulator 30 and the electrode 32, as shown. Such spark plug structure is standard and forms no part of the present invention.

The spark plug lead wire 14 may be any of the known automobile spark plug lead wires and. as shown. has a connector 34 secured to the end thereof adapted to receive one end of the radiation suppression resistor 16.

The radiation suppression resistor 16 is also known and may be any of a plurality of wire wound resistors. It is connected at one end to the spark plug lead wire 14 by the connector 34 as indicated above. The radiation suppression resistor 16 is connected to the sleeve 38 at the other end. The sleeve 38 is adapted to fit over the electrode 32 of the spark plug 12 to make electrical connection therebetween.

As shown, insulating material 40 and insulating boot 42 are provided around the ends of the spark plug lead wire 14, the connector 34, radiation suppression resistor l6 and sleeve 38 to prevent shorting of the ignition voltage and to hold the spark plug lead wire 14, radiation suppression resistor 16, connector 34 and sleeve 38 in assembly. Again, such structure is known and does not in itself form part of the present invention.

The high frequency radiation suppression shield 10 of the invention includes the boot 44 which, as shown in FIGS. l-3, is a single cylindrical member having a closed end 46 with an opening 48 extending therethrough through which the spark plug lead wire 14 extends and an open end 50 through which the metal screen portion 52 of shield 10 extends into engagement with the shell 20 of the spark plug 12.

plug 12, the radiation suppression resistor 16. and the connecting means therefor including the connector 34 and the sleeve 38, The screen 52 may be of aluminum wire. for example. n

Thus. in operation. on a high voltage being applied through the spark plug lead wire l4 to the terminals 24 and 26 o f the spark plug 12 through the radiation suppression resistor 16. a'spark is'initiated within the chgine block 18 and high frequency' radiations tend to emanate from the adjacent ends of the spark plug lead wire 14, spark plug 12. and the radiation suppression resistor 16. These high frequency radiations are either confined to an area relatively substantially insideof the 7 high frequency shield formed by the screen 52 or are shorted to ground through the screen 52 and the spark plug 12 to the engine block 18.

In practice. the electromagnetic noise radiated in a normal automobile ignition circuit due to the'firing of the spark plug 12 is greatly reduced. Further. it will be noted that the boot 44 with the screen "52'molded therein is particularly simple in construction and economical to manufacture. as well as being efficient in use. Thus. for example, the shield-l does not prevent removal andieplacement of the connection between the spark plug lead wire-14 and the spark plug 12 during. for example. normal tune-up andservicing of an automobile and will'not become misplaced during-such connecting and disconnecting since the shield is secur ed on the spark plug lead,'wire 14. It will also be notedthat no special tools are required for the installation'of the shield 14, andthat due. to the construction of the shield, itis not subject to damage due to deformation and the like. Further, due to the particular construction of the high frequency radiation suppression shield 10, when the connection is made between the spark'plug terminal 32 and sleeve 38, as itmust be for the spark plug to fire. the shield is automatically groundedwith the screen 52 extendingthrough the boot 44 in engagement with the shell 20 of the spark plug 12, whereby, any time the spark plug l2'is connected to fire, the high frequency suppression shield 10 is active. I

As shown best in-FlG. 4, the shield 10 is easily adaptable to ignition circuits wherein the axis 54 of the lead may be advantageously constructed of a first outer cylindrical member 60 of silicone in which the screen 62 is molded. A second spacing cylinder 64 is provided betweenthe cylinder 62 and the usual insulating material 42 surrounding the end of the spark plug lead wire 14, spark plug 12, radiation suppression resistor 16, and connecting means therebetween. With such coaxial cylindricalfconstruction. 'a generally circular end cap 66 is provided having the cross'section shown in H6. 5 for receiving one end of the cylinder 60.

While one embodiment of the present invention has been considered in'detail and embodimentsand modifcations thereof suggested, it will be understood that other embodiments and modifications of the high frequency radiation suppression shield of theinvention are contemplated. ltis therefore intended to include all such embodiments and modificationsas are defined by the appended claims within the scope of theinvent ion.

What I claim as my invention is: i i

1. In combination, a spark plug for an automobile ignition or the like, a spark plug lead wire for high voltage electricalenergy, means connecting one end of the lead wire to one end of the spark plug for intermittent transferof energy from the lead wire to the spark plug. an insulating boot surrounding the one end of the lead wire and the one end of the spark plug, and a conductive shield molded into the boot for suppressing high frequency radiation from the one end of the spark plug and the one 'end of the lead wire with the spark plug in use, said shield extending through one end of the boot at a plurality of spaced'points around the periphery thereof and into contact with the base of the sparkplug at a plurality of spacedpoints around the periphery thereof to provide a ground connection for the shield,

said boot being at least'a two-piece member including further includes another cylindrical member positioned within the first cylindrical member;

. 4. Structure as set forth in claim l,,wherein the axis of the spark plug lead wire and the axis of the spark plug are positioned at an angle to each other and the boot has the same angle therein.

5. Structure as set forth inclaim l,'wherein the axis of the spark plug lead wire and the spark plug are co linear and the boot is straight. I t

6. Structure as set forth in claim 1 and further including a radiation suppression resistor positioned between the spark plug lead wire and spark plug. 

1. In combination, a spark plug for an automobile ignition or the like, a spark plug lead wire for high voltage electrical energy, means connecting one end of the lead wire to one end of the spark plug for intermittent transfer of energy from the lead wire to the spark plug, an insulating boot surrounding the one end of the lead wire and the one end of the spark plug, and a conductive shield molded into the boot for suppressing high frequency radiation from the one end of the spark plUg and the one end of the lead wire with the spark plug in use, said shield extending through one end of the boot at a plurality of spaced points around the periphery thereof and into contact with the base of the spark plug at a plurality of spaced points around the periphery thereof to provide a ground connection for the shield, said boot being at least a two-piece member including a cylindrical member having one end at the one end of the boot and having the screen molded therein and a cap surrounding the one end of the lead wire and receiving the other end of the cylindrical member.
 2. Structure as set forth in claim 1, wherein the boot is constructed of a high temperature silicone.
 3. Structure as set forth in claim 1, wherein the boot further includes another cylindrical member positioned within the first cylindrical member.
 4. Structure as set forth in claim 1, wherein the axis of the spark plug lead wire and the axis of the spark plug are positioned at an angle to each other and the boot has the same angle therein.
 5. Structure as set forth in claim 1, wherein the axis of the spark plug lead wire and the spark plug are co-linear and the boot is straight.
 6. Structure as set forth in claim 1 and further including a radiation suppression resistor positioned between the spark plug lead wire and spark plug. 